A friend of mine visited a Central American country (not Mexico) recently, to visit other friends who had moved there to join an English language congregation.
The "use" of Witness "Bible" studies merely to learn English was so rampant that the "local needs" part on the service meeting, while my friends were there, was on being "discerning" when conducting Bible studies. "We're not here to teach people English, we're here to teach them the Bible".
So the issue of "the natives" looking to get free English lessons as a means to make an escape to better economic conditions appears to be quite widespread.